It's the French way and was frowned on by my granny for that reason. However, I started using it when doing maths and physics at A-Level where it was pretty useful to make sure your equation made sense.

I mean these were the 80s for one thing, but she objected to it in the same way that I object to people using 'license' when they should write 'licence', or indeed as many other pieces of US Cultural imports are viewed by people.

I think natural (mainly jovial) dislike of the French (reciprocated) was a big thing throughout most of the 20th C, two world wars aside. :)